Method of preparing substantially pure free mahogany sulphonic acids



Patented Aug. 2, 1938 METHOD OF PREPARING SUBSTANTIAILY PURE ma SULPBONIC AC- IDS GeorgeAndreasxesslcrandLeosalsmanmBut ler,la.,assignorstoL.Senneborn8ons,lnc., acorporationofnelaware No mm. Application October 0, ms, Serial No. 104.1 s

This invention relates to a new and useful method of preparing substantially pure free mahogany honic acids. The conventional refining tr' ment of certain lubricating oil distillates derived from petroleum includes the application of fuming sulphuric acid. 'Ihis reacts with the oil, producing a black sludge containing unreacted sulphuric acid and certain types of sulphonic acids. Though the concentration of 10 SO; in the turning acid may vary considerably, a 20% fuming acid is employed in the majority of cases. As a result of the high degree of sulphonation obtained in the acid treatment, a considerabie amount of sulphonic acids is. produced.

These are principally of two types, that is, the

so-called water-soluble type predominantly contained in the sludge and the so-called oil-soluble type predominantly found in the oil to the extent of a few percent. The acid application is regulated in the manner well known in the art to produce the desired sulphonation reaction and in general temperatures not exceeding 140 1". are

preferred. The acids contained in the sludge, while limitedly soluble, if stall, in hydrocarbon g5 oils, are highly water soluble, imparting to their aqueous solution a dark-green color, and being for this reason generally referred to as green petroleum sulphonic-acids. The acids left in solution in the oil impart areddish color to the oil and for this reason are generally referred to as mahogany petroleum sulphonic aci After; the separation of the oil from the acid sludge th'e mahogany sulphonic acids'are removed irom the oil either directly as such in accordance with the method described in the Liberthson Patent 2,050,345 (Aug. 11, 1936), or by the ordinary refining method comprising conversion'of the acids into salts by direct neutrali tion of the acid treated oil followed by suitable extraction. The 0 acid salts or mahogany sulphonates constitute a valuable by-proditct of petroleum refining, being i used aiteriurther purification, if necessary, for a variety of purposes, but primarily as emulsify ing agent.

' For certain purposes it is desirable to obtain the free mahoganysulphonic acids in a substan-, tially pure state. So, for instance, where for special purposes it' is desired touse free acids instead ,of the sodium salts, or to prepare esters and salts of various. organic and inorganic bases. Hitherto it has not been possible to accomplish this result in any satisfactory manner as .it is extremely difilcult to obtain a product substantially free from sulphuric acid and salts.

a We have discovered that these,

6 Claims. (Cl. 260-159) in the solvent. We have found that suitable solvents of this nature are, for instance, petrol ether, gasoline, benzol and its homologues, chlorinated hydrocarbons, and others of a like character.

In accordance with the invention hydrochloric acid gas is-passed through a substantially acidfree solution of mahogany sulphonate in a suitable organic solvent of the store-described nature. A color change from orange to red will beobserved together with salt precipitation. j The metal component of the sulphonate, in most cases sodium, is replaced by the hydrogen of the hydrochloric acid, thus forming a metal chloride. The reaction is accompanied by considerable heat development. The solution, separated from undissolved inorganic matter by settling, filtration, centrifuging or the like, yields after the evaporation of the solvent the free sulphonic acids in the form of a dark reddish syrup. Inasmuch as dissolution of the mahogany sulphonate will precipitate ab initio any salt originally present in the sulphonate, a crude mahogany sulphonate same from any salt content that it may possess.

may be used, and it is not necessary to free the It is requisite, however, that the sulphonate be substantially free from sulphuric acid. Any excess hydrochloric acid dissolved in the solvent is removed simultaneously with theevaporation of the solvent.

We have found that sometimes, though there is a color change from orange to red in the solu-.

it of. advantage to maintaina moisture content of approximately 1% within the solution.

Though the free acids obtained in this manner are substantially pure, some of the salt produced during the reaction is still sumciently dissociated as the result oithe moisture content and will escape nitration; So, for instance, a moisture content of approximately 1% will give on analysis an ash residue of about 0.17%, indicating that some saltwas retained by the mahogany sulphonic acid. We have discovered that we can eliminate the last traces oi any such salt, obtaining upon analysis a product absoluteiy'iree from any ash residue, by adding a slight percentage of a suitable aliphatic alcohol such as methyl, ethyl, propyl, butyl or similar alcohol but preferably about 1% of ethyl alcohol to the solution of themahogany sulphonate.

In the practical application of our method we preferably employ a 25% solution of acid-free mahogany sulphonate, containing approximately tially complete pfecipitation ot the salt.

.presence of excessive amounts otwater should 5%; water in a suitable solvent such as gasoline orifpetrol ether. The hydrochloric acid gas is preferably passed in a dry state through this solutionLL: Inthis manner the moisture content can be more easily regulated and limited to the amount just suflicient to eflectuate'the substanbe avoided as these cause a partial redissolution oi the precipitated salts, thereby increasing the amount of salt retained by the free acid after the eaporation of the solvent. Due to the rather unstable character of the mahogany sulphonic acids at higher temperatures, it is of advantage to conduct the evaporation of the solvent by vacuum distillation. 7' The ioregoing' description is by way of illustration and not or limitation, and we are not to be limited to a detailsbut only by the appended claims in whi *we have endeavored to claim broadly all inherent novelty.

We claim: 1 l I 1; Method of preparing pure iree mahogany sulphonic acids which comprises passing gaseous hydrochloric acid through a solution 01' mahogany sulphonates, substantially free from involatile inorganic acids; in a substantially water immiscibleiorganic solvent therebyi'orming a soiu-- tion of tree mahogany sulphonic acids and unnissolved inorganic salts thereafter separating 'said inorganic salts from said solution and finally removing the, solvent from the; solution of the tree mahogany sulphonic acids saidsolvent being substantially incapable of dissolving inorganic salts, and said gseous being passed tlsrough said solution of mahogany sulphonates in amount sumcient to convert substantiaiiy all on said mahogany sulphonatesinto free mahogany sulphonic acids.

2. Method of preparing pure tree mahogany sulphonic acidswhich comprises passing gaseous hydrochloric acid through a solution oi. mahogany siilphonates, substantially iree'irom involatile inorganic acids, in a substantially water immiscible organic solvent thereby forming a solution of 1 free mahogany sulphonic acids and undissolved inorganic saitswhile substantially maintaining in said solvent a moisture content sumcient to suit;- stantially' congplete' the reaction .between said hydrochloric acid and said mahogany sulphonates, thereafter separating said inorganic salts from said solution and iinallyremoving the solvent from the solution-g oi the tree mahogany sulphonic acids. 581d solvent being substantially incapable of dissolving inorganic salts, and said gaseous hydrochloric acid being passed throughsaid solution of mahogany sulphonates in-amount suflici'ent to convert substantially all c saidmar hydrochloric acid amasoo hoga ny suiphonates into free mahogany sulphonic chioric acid being passed througlrsaid solution 0! mahogany suiphonates in, amount suflicient to convert substantially of said mahogany sulphonates into free mahogany sulphonic acids.

4. Method ofzpreparlng pure tree mahogany sulphonic acids which comprises passing gaseous hydrochloric sold through a solution oi! mahogany sulphonates, substantially free from involatile inorganic acids, in a substantially water immisci ble organic solvent containing an aliphatic alcohol, thereby forming a solution of free mahogany sulphonic acids and un'dissolved inorganic salts while substantially maintaining in said solvent a moisture content suiilcient to substantially complete the reaction between said hydrochloric acid and said mahogany sulphonates, thereafter sepe arating said inorganic salts from said solution and ilnally removing the solvent from the solution of the tree mahogany sulphonic acids, said solvent, being substantially incapable of dissolving inorganic salts, said. aliphatic alcohol being present in amount suh'icient to eilectuate a substantialiy complete precipitation of inorganic salts formed in said solution, said gaseous hydrochloric acid being passed through said solution of mahmny sulphonates in amount sufllcient to convert substantially all of said mahogany suiphonatcs into free mahogany sulphonie acids.

5. Method of preparing pure tree mahogany sulphonic acids which comprises passing gaseous hydrochloric acid through a. solution of mahogany sulphonates, substantially free from involatile inorganic acids. in a substantially water immiscible organic solvent and containing'substantially 1%;0! ethyl alcohol thereby forming a solution of free mahogany sulphonic acids and undisolved. inorganic salts while substantially maintaining in said solvent a moisture content sumcient to substantially complete the reaction between-said hydrochloric acid and said mahogany sulphonates. thereaiter separating said inorganic salts from said solution and finally removing the solvent from the solution of the free mahogany snlphonic'acids, said solvent being subin eapable'ot dissolving inorganic salts, and'fsaid gaseous hydrochloric acid being passed through said solution oi mahogany sulphona'tes in amount suiiicient to convert substantially all of said mahogany sulnhon tes into free ma hogany sulphonic acids. 1

6.1lethod of preparing time free mahogany sulphonic acids which comprises passing gaseous hydrochloric acid through a solution of mahogany j sulphonates, substantially free from involatile inorganic acids, in a substantially water immiscible organic solvent and containing substantially: 1% 01' ethyl alcohol thereby i'orming a sc iution ofiree mahogany sulphonic acids and unnissolved inorganic salts. while. maintainingin amaaoo 3 said solvent a" moisture content of 1% thereafter separating said inorganic salts from said solution and finally removing the solvent from the solution of the free mahogany sulphonic acids, said solvent being substantially incapable of dissolving inorganic salts, and said gaseous hydrochlorlcacid being passed through said solution of mahogany sulphonates in amount sumcient to convert substantially all of said mahogany sulphonates into free mahogany sulphonic acids. 

